Authorization Proxy for SPARQL Endpoints

A large number of emerging services expose their data using various Application Programming Interfaces (APIs). Consuming and fusing data form various providers is a challenging task, since separate client implementation is usually required for each API. The Semantic Web provides a set of standards and mechanisms for unifying data representation on the Web, as well as means of uniform access via its query language - SPARQL. However, the lack of data protection mechanisms for the SPARQL query language and its HTTP-based data access protocol might be the main reason why it is not widely accepted as a data exchange and linking mechanism. This paper presents an authorization proxy that solves this problem using query interception and rewriting. For a given client, it solely returns the permitted data for the requested query, defined via a flexible policy language that combines the RDF and SPARQL standards for policy definition.